A report on IBM Personal Computer and Industry Standard Architecture

IBM PC compatible computers are similar to the original IBM PC, XT, and AT that are able to use the same software and expansion cards.

It was later re-named the Industry Standard Architecture (ISA) bus, after the Extended Industry Standard Architecture bus open standard for IBM PC compatibles was announced in September 1988 by a consortium of PC clone vendors, led by Compaq and called the Gang of Nine, as an alternative to IBM's proprietary Micro Channel architecture (MCA) introduced in its PS/2 series.

Compaq produced some of the first IBM PC compatible computers, being the second company after Columbia Data Products to legally reverse engineer the IBM Personal Computer.

Although Compaq had become successful by being 100 percent IBM-compatible, it decided to continue with the original AT bus—which it renamed ISA—instead of licensing IBM's MCA.

In the original IBM PC (and the follow-up PC/XT), there was only one Intel 8237 DMA controller capable of providing four DMA channels (numbered 0–3).

With the IBM PC/AT, the enhanced AT Bus (more familiarly retronymed as the ISA, or "Industry Standard Architecture") added a second 8237 DMA controller to provide three additional, and as highlighted by resource clashes with the XT's additional expandability over the original PC, much-needed channels (5–7; channel 4 is used as a cascade to the first 8237).

A single 8237 was used as the DMA controller in the original IBM PC and IBM XT.

For example, the PIIX integrated two 8237 controllers for ISA bus DMA.

The Datamaster was the least expensive IBM computer until the far less expensive and far more popular IBM PC was announced in the following month.

The PC's expansion bus, later known as the ISA bus, was based on the Datamaster's I/O bus.

The 8259A was the interrupt controller for the ISA bus in the original IBM PC and IBM PC AT.